Well, I pulled my engine and removed the cylinder heads. There seems to be some carbon build up on the top of the pistons. Should I removed the carbon build up or leave it alone? and if so, what is the best method of removing it?
engine has 113,000 miles.
Gasket scraper, brake cleaner, and elbow grease. You could get a wiz wheel or something just make sure you put the piston at top dead center and don't scratch up the cylinder walls. Don't worry about the piston, short of a cutoff wheel you won't hurt those.
Wire brush as much off as you can. Then get either paint remover or spray gasket remover (paint remover in a spray can) and put it on the carbon. It will melt that carbon right off in minutes. It also works great for cleaning garbage out of carburetors.